DESCRIPTION: A new technique, called Hartmann wavefront sensing, will be used to measure the aberrations of the human eye. With a single flash, this automated technique can provide a complete description of the eye's aberrations, including irregular aberrations that have not been characterized before. The effect of irregular aberrations on the quality of the retinal image can be determined for the first time. The wavefront sensing technique may improve autorefraction, contact lens design, and the evaluation of outcomes following ocular surgery. A new, high- resolution fundus camera will be constructed that is equipped with adaptive optics. The camera will automatically measure the wave aberration with a Hartmann wavefront sensor and then correct it with a deformable mirror.When acquiring fundus images through a 6 mm pupil, this camera should provide a 3-fold increase in transverse resolution and a 9-fold increase in axial resolution over conventional fundus imaging. The instrument should be capable of resolving retinal structures as small as foveal cones or the larger fibers in the nerve fiber layer in the living human eye. The nature of the light reflection from single cones in the living human fundus will be determined. Ultimately, the device may be useful in characterizing photoreceptor pathology in vivo. Adaptive optics can also provide an observer with better retinal image quality than he/she has experienced. We will measure visual performance when observers view natural stimuli through a deformable mirror that corrects the wave aberration of the eye. These measurements will clarify the relationship between optical and neural factors in spatial vision.